Vojislav M. Petrović

Vojislav M. Petrović was born in Mala Kamenica, a small Serbian town near Negotin, in 1925. After graduating from the Department of Biology at the School of Natural Sciences at the University of Belgrade in 1953, he worked as a high school teacher in Negotin for a short period before he was employed at the School of Natural Sciences in Belgrade. After successfully defending his Ph.D. thesis, entitled “Endocrine Factor of Thermoregulation and Thermal Adaptation”, in 1959, he became deeply involved in the scientific field of Animal Physiology, becoming one of the most distinguished members of the Belgrade School of Physiology.

Thanks to the significant results in his doctoral thesis, professor Petrović earned the opportunity to spend one year in Paris at the College de France, Laboratorie de Endocrinologie as a postdoctoral fellow of the Andre Mayer Foundation and the French Academy of Sciences in Strasbourg. At the invitation of the National Research Council in 1967, he spent one year in Canada as a visiting researcher, working on a joint project dealing with endocrinology and thermal regulation (Marinkovic, 2007).

He was elected assistant professor at the University of Belgrade in 1960, an associate professor in 1968 and a full professor in 1974. He founded the Chair for Comparative Physiology and Ecophysiology at the Department for Biological Sciences (currently School of Biology) of the School of Sciences at the University of Belgrade. He headed the Department until his retirement in 1993. He was also the founder and head of the Department of Endocrinology and Metabolism (currently Department of Physiology) at the Institute for Biological Research “Siniša Stanković” at the University of Belgrade. (Davidovic, 1998). Students eagerly attended and carefully followed professor Petrović’s lectures. He published over 20 university textbooks (including “Comparative Physiology I” in 1991; “Comparative Physiology II”, in collaboration with R. Radojičić, in 1993; and “Endocrinology: General and Comparative”, in collaboration with G. Cvijić, in 1997), high-school textbooks and professional books.

Some of Professor Petrović’s major research interests were neuroendocrine regulation and neurosecretion in disturbed homeostasis, the effect of hormones on molecular processes, thermoregulation, thermal adaptation and stress, biological rhythms and hibernation, and the mechanisms of redox regulation and cellular antioxidative defenses. He published over 200 scientific papers in these topics, which have been cited more than 600 times.

His research on response to high external temperatures (in the thermolysis zone) showed that homeotherms first respond with an array of characteristic changes in the neuroendocrine system, which are reminiscent of alarm state behavior: the sympathetic tonus is increased, animals are disturbed, the catecholamine content in the adrenal glands is decreased and accompanied by their increased excretion, and adrenocortical activity is increased. The enzymatic activities of tyrosine hydroxylase (TH) and phenylethanolamine-N-methyltransferase (PNMT), which regulate catecholamine synthesis, are also increased. These results were the first to point to the nonspecific response of homeotherms exposed to high ambient temperatures (Petrovic et al., 1976). These studies led to a new theory about the nonspecific response in the alarm phase and attracted particular attention among his peers in the field. In fact, these results pointed to opposite bioenergetic demands in homeotherms exposed to the zone of thermolysis with respect to thermogenesis in cold conditions, although at first they respond in the same way. At the Symposium on stress held in Monte Carlo in 1979, organized by the Canadian Institute headed by Hans Selye, professor Petrović was invited among a few dozen scientist including six Nobel price winners. Discussing Petrović’s results Hans Selye commented “the best proof for nonspecific response to stressors that I have seen so far”.

Relative to the scientific subtopic of the sympatho-adreno-medullar system and its adaptation to changes in the thermal conditions of the environment, Professor Petrović’s results showed that homeoterm’s direct response to cold depends on the activity of sympathetic nervous system, as well as the medulla and cortex of the adrenal glands. Sympathetic tonus under these conditions is increased, resulting in the involuntary muscular movements of shivering, which is expressed as heat production due to respiration and phosphorylation processes. The biological rationale of these changes is to maintain homeostasis. Most of the shivering thermogenesis occurs during the first several days of exposure to cold conditions, after which it gradually decreases, accompanied by a compensatory increase in non-shivering thermogenesis. Both hormones of the adrenal medulla, epinephrine and norepinephrine, take part in the thermogenic “response” of homeotherms to cold. These hormones stimulate glycolysis and lipolysis, thus providing energy-rich compounds for further biochemical transformation in the most thermogenicaly active tissues. Under these conditions, the quantity of both stated catecholamines in the adrenal glands is decreased and their secretion as well as that of their metabolites, such as vanilmandelic acid, is increased.

Ground squirrels exposed to cold in the summer exhibit changes in the activities of adrenal TH and PNMT. Petrović proved that these changes are the result of neuronal and hormonal control. Specifically, cortical glucocorticoids stimulate the activity of PNMT, the enzyme responsible for epinephrine synthesis; adrenocorticotrophine is involved either directly or indirectly in the regulation of TH and PNMT activity. As treatment with metopirone and dexamethasone affected PNMT activity but did not alter TH activity, it can be assumed that hormonal factors dominate in the control of PNMT activity (Fig. 4). It seems that neural factors dominate in the control of TH activity (Petrovic and Janic Sibalic, 1976).

In early 1970s, professor Petrović recognized the importance of the study of free radicals, particularly superoxide anion radicals and antioxidative defenses, which at that time was in its infancy. It was a logical choice after his long period of research in mitochondria, given that the highest production of superoxide anion radicals occurs in the respiratory mitochondrial chain. Professor Petrović’s research group was the first to publish on the activity and distribution of CuZn superoxide dismutase in the tissues of hibernators. This work empirically suggested that the increase in the antioxidative defense SOD activity in the tissues of a hibernator (Citellus citellus) during hibernation, when metabolism and oxygen consumption is decreased, results from preparation for the waking phase, when metabolism intensity and oxygen consumption increase precipitously over a short period of time (particularly in thermogenically active tissues). This became an unavoidable reference in all works dealing with hibernation, given that it produced the first data of that kind (Petrovic et al., 1983). Later on, the proposed mechanism was confirmed by other authors using different parameters. It was also shown that the same mechanism of preconditioning is employed for the needs of both waking from hibernation and for other states that lead to increased metabolism and oxygenation (Petrovic et al., 1983).

In parallel with his highly successful scientific and teaching work, Professor Petrović was eagerly committed to various other academic activities. He was a vice dean (1969) and a dean (1971) of the School of Natural Sciences at the University of Belgrade, head of the Department for Biological Sciences of the School of Natural Sciences (1973) and, together with professors R.K. Andjus and D. Kanazir, he greatly contributed to the establishment of a new study group at his Faculty: Molecular Biology and Physiology, the first such group in former Yugoslavia.

In 1974, he was elected to be the corresponding member of the Serbian Academy of Sciences and Arts; from 1975–1979, he became vice-rector, and from 1981–1985, he served as rector of the University of Belgrade. Between these two elections, he held the position of the Director of the Institute for Biological Research in Belgrade. He was a member of the Bureau of the European Standing Conference of Rectors (ad personam), a member of the Bureau of the Danube Rectors’ Conference, a member of the Higher Education Commission at the European Council in Strasbourg, President of the Education Council of Serbia, and a member of the Federal Committee for Science and Technology, SFR Yugoslavia. In 1986, he was elected full member of the Serbian Academy of Sciences and Arts. He was a member of the Presidency of the Serbian Academy of Sciences and Arts and President of its Board for Biology in the Department of Chemical and Biological Sciences and a member of the Inter-Departmental Boards for Biomedicine and Ecophysiology. Professor Petrović died in 2007.